1. Field of the Invention
The present invention relates to an electro-magnetic or dynamoelectric device, and more particularly to a new housing for such a device which includes a central housing and a pair of end members wherein the central housing is dimensionally stable, accurate and does not require extensive machining of the central housing or end members.
Electro-magnetic couplings of the type are well known in the art and include a rotor which is disposed within a rotatable inductor drum. A coil is energized to generate a field which electro-magnetically couples the rotor and drum so that torque may be transferred therebetween. The rotor, inductor drum and coil are all located and supported by a housing assembly. The mounting of the inductor drum relative to the rotor is critical in that a dimensionally stable air gap must be maintained therebetween to allow for relative rotation of the inductor drum and rotor and across which the field must pass. Additionally, the rotor and inductor drum member must be supported within the housing to allow relative rotation therebetween without interfering with the housing. The concentric mounting of the rotor member, inductor drum and coil typically require conventional housings that are machined to a tolerance in the area of plus or minus one thousandth of an inch. The conventional housings are usually fully machined housings of a casting or heavy weldment. The prior art results in a structurally sound, dimensionally accurate and quite expensive housing. The present invention describes a new and improved housing to achieve adequate structural rigidity and dimensional accuracy at a greatly reduced cost by using a one piece mandrel formed sheet steel design for the central portion of the housing.
2. Prior Art
The Jaeschke U.S. Pat. No. 4,362,958 discloses a typical electro-magnetic coupling and a housing therefore wherein the housing is machined to tight tolerances.
The Kohler Company manufactures a portable gasoline powered alternator which uses a similarly shaped housing which has a cross sectional configuration substantially identical to the cross sectional configuration of the present housing. However, Kohler does not utilize a housing which expands in a radial direction to obtain a zero clearance pilot fit. Kohler utilizes an alternator stator which is pressed into the housing before the end brackets are installed thereby preshaping the housing. This precludes any further reshaping of the housing by the end brackets or expansion of the housing in a radial direction upon insertion of the end members. In the Kohler housing, the length of the housing is about equal to the diameter. Also, the stator which is press fitted into the housing is disposed adjacent the end of the housing. Thus, press fitting the stator into the housing preshapes the housing and there is not enough metal extending from either side of the housing away from the stator to allow the end members to reshape the housing.
The Allendorph Pat. No. 3,321,654, discloses a dynamoelectric machine frame which utilizes a sheet steel housing. Allendorph has a generally circular construction which slightly deforms when the stator is fitted therein. The insertion of the end frames returns the housing to a circular form. The use of a circular housing limits the interference fit that can be utilized due to the circular configuration of the housing. Allendorph has a maximum of 0.005 inches interference fit between the end frames and the central portion of the housings.